1. Field of Invention
This invention relates, generally, to process for producing organic tetravalent tin polyhalide. More particularly, it relates to a method for refining a mixture of tin halides to obtain a higher yield of the desirable tin polyhalides. The organic tetravalent tin polyhalides are useful as starting materials as a stabilizer for polyvinyl polymers, as polymerization catalyst for the production of polyurethane, and as a builder of a coating film of tin oxide on glass, ceramics, and metals.
2. Description Of Related Art
The commonly know aluminum process in which stannic chloride reacts with alkyl aluminum, the commonly known Grignard Process in which the Grignard regent reacts with stannic chloride, and the commonly known Direct Process in which achyliodide directly reacts with metallic tin have been known as the prior art production methods for producing organic tetravalent tin polyhalides, that is the tin compound whose valence is 4, rather that 2. In both the Aluminum Process and the Grignard Process the corresponding chlorides are formed as intermediate compounds, and in the Direct Process the corresponding iodide is also formed as a intermediate.
For example, dialkyl tin dichloride, one of the polyhalides which can be synthesized by Alkyl Aluminum or Grignard process via tetraalkyl tin (IV) as an intermediate, is disproportionately reacted with equimolecular stannic chloride. Dialkyl tin (IV) diiodide can be synthesized by the Direct Method in which alkyl iodide and metallic tin are reacted with metallic magnesium and alcohol as a catalyst. However, the dialkyl tin (IV) dihalide synthesized by these methods always contains significant amounts of trialkyl tin monohalide and monoalkyl tin trihalide as by-products.
Therefore, it is desirable to eliminate organic tin monohalides from its corresponding polyhalides because it is well known that organic tin monohalides commonly higher toxic than its corresponding polyhalides.
It may be possible to reduce the organic tin monohalide contained in organic tin polyhalide by addition and heating treatment with excess anhydrous stannic chloride for the monohalide and, as a catalyzer, aluminum chloride. However, this process is very expensive and difficult, because of its non-selectivity of the reaction and the disposal requirement for hydroxides formed from stannic chloride involved in the main reaction and from aluminum chloride. Additionally, the monohalide is difficult to eliminate from monoalkyl tin polyhalide by distillation because the boiling point is too close in each other. There are no prior methods reported to eliminate economically a small content of trialkyl tetravalent tin monohalide from monoalkyl tetravalent tin trihalide and dialkyl tetravalent tin dihalide which are similarly synthesized.
Although a decomposition reaction from organic tin monohalide to the polyhalide by hydrochloric acid or chlorine was described in Metal-Organic Compound, item 208 or Chemical Review Vol. 60, item 483, no example to eliminate organic tin monohalide in the polyhalide is shown.
3. Summary of the Invention
This invention relates to a process of treating organic tetravalent tin polyhalide which contains organic tetravalent tin monohalide with hydrochloric acid, hydrogen chloride or chlorine for refining organic tin polyhalide, to selectively decompose and transform organic tetravalent tin monohalide to organic tetravalent tin polyhalide. Furthermore, the reaction efficiency of the present invention can be remarkably improved by the addition of Lewis acid.
Illustrative equations for the reaction between organic tin monohalide and hydrochloric acid, hydrogen chloride or chlorine in this invention are as follows:
1) R.sub.3 SnX+HCl - R.sub.2 SnXCl+RH PA1 2) R.sub.3 SnX+Cl.sub.2 - R.sub.2 SnXCl+RCl PA1 R is alkyl or phenyl, and, PA1 X is chlorine, bromine, or iodine PA1 R is alkyl or phenyl, and, PA1 X is chlorine, bromine, or iodine
wherein, R=alkyl or phenyl, and X=chlorine, bromine, or iodine. As shown, organic tetravalent tin dihalides and organic tetravalent tin trihalides are co-produced with organic tetravalent tin polyhalides in the invention.
Dibutyl tin dichloride, dibutyl tin diiodide, di-butyl tin dibromide, dioctyl tin dichloride, dioctyl tin diiodide, dioctyl tin dibromide, diphenyl tin dichloride and diphenyl tin diiodide can be given as the examples of organic tetravalent tin dihalides. Butyl tin trichloride, butyl tin triiodide, butyl tin bromide, octyl tin trichloride and octyl tin triiodide can be also given as the examples of organic tetravalent tin trihalides. Organic tin monohalide in the invention is defined as the corresponding monohalide to each dihalide or trihalide previously given; then, tributyl tin monochloride, tributyl tin monoiodide, tributyl tin monobromide, trioctyl tin monochloride, trioctyl tin monoiodide, trioctyl tin monobromide, triphenyl tin monochloride and triphenyl tin monoiodide can be given as the examples of the organic tetravalent tin monohalide.
Concentration of hydrochloric acid used in the inventive process is higher than 20%; preferably about 35% is desirable. Either dried or wet hydrogen chloride gas or chlorine can also be usefully applied.
Proper conditions for the method of this invention is a temperature which is dependent upon the type of organic tin polyhalide. The higher temperature results in higher efficiency, but due to undesirable side reaction, such as organic tin dihalide decomposes to organic tin trihalide at temperatures beyond 250.degree. C. Therefore, it is preferable to use a temperature between 100-200.degree. C. Quantity of reacted hydrochloric acid, hydrogen chloride or chlorine depends upon the type of treated organic tin polyhalides. Thus, about 1-100 times on the molar basis of the organic tin monohalide is a reasonable ratio, preferably 20-50 times molar. Most of hydrochloric acid, hydrogen chloride or chlorine can be recovered, so its net quantity consumed through the reaction is very slight.
According to the inventive method, the reaction procedure comprises organic tin polyhalide which is mixed already with hydrochloric acid is slowly heated under stirring conditions or the latter is dropped into the former already heated. In this case higher contact efficiency of the stirring is desirable. In the reaction with hydrogen chloride or chlorine, it is introduced as a gas into already heated organic tin polyhalide admixture which is to be refined. In this case the higher contact of the gas with the reacting solution is also desirable; therefore, location at where the gas is introduced is more desirable to be inside of liquid organic tin polyhalide mixture than at its surface. Contact time is preferably 2 to 3 hours; 1 to 2 hours; and 10 minutes to 1 hour in the case of hydrochloric acid, hydrogen chloride or chlorine, respectively. The content of organic tin monohalide in the polyhalides is reduced to be less than 10 ppm by the method of this invention.
A catalyst is not necessary in the practice of this process, but the reaction is effectively accelerated by a slight addition of Lewis acid. Most of all Lewis acid widely known are useful, for example AlCl.sub.13, AlBr.sub.3, AlI.sub.3, GaBr.sub.3, GaCl .sub.3, FeCl.sub.3, SbCl.sub.5, SnCl.sub.4, SnI.sub.4, ZnCl.sub.4, BCl.sub.3, BF.sub.3, and ZnCl.sub.3 ; the most preferable of these is AlCl.sub.3 because of its lower expense and higher effectiveness.
As a further embodiment of this invention the refined organic tetravalent tin polyhalide is successively hydrolyzed to organic tin oxide, which is further less contaminated by organic tin monohalide. The hydrolysis is carried out according to a method, for example, described in Japanese Pat. No. Sho 61-291592 (1986).
Thus, the disadvantages of the prior art are overcome by the inventive method which comprises a method for producing an organic tetravalent tin polyhalide which comprises contacting an admixture of organic tetravalent tin polyhalide and organic tetravalent tin monohalide with hydrochloric acid, hydrogen chloride or chlorine in an amount and under condition sufficient to convert the organic tetravalent tin monohalide to organic tetravalent tin polyhalide. A further embodiment of the invention includes a method for producing an organic tetravalent tin polyhalide which comprises contacting an admixture of an organic tetravalent tin polyhalide of the formula EQU R.sub.2 S.sub.N X.sub.2 (A)
wherein
and an organic tetravalent tin monohalide of the formula EQU R.sub.3 S.sub.N X (B)
wherein
with hydrochloric acid, hydrogen chloride, or chlorine in an amount from 1 to 100 moles per mole of (B) and at a temperature from 100.degree. to 250.degree. C. sufficient to convert (B) to (A). A specific embodiment of this invention comprises a method for producing an organic tetravalent tin polyhalide which comprises (a) the process of reacting a tetravalent tin halide with organoaluminum, a Grignard agent, or the process of reacting metallic tetravalent tin with an organohalide, thereby producting a reaction product comprising an organic tetravalent tin polyhalide and by-product organic tetravalent tin monohalide, such process does not include the removal of the by-product, (b) contacting the reaction product with hydrochloric acid, hydrogen chloride or chlorine in the presence of Lewis acid catalyst under conditions sufficient to convert the by-product to organic tetravalent tin polyhalide, and, (c) recovering organic tetravalent tin polyhalide.